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1500 questions
14
votes
4 answers
What does the addition of a shield to a small loop accomplish?
A small shielded loop is an antenna with a loop of wire, smaller than 1/10th of a wavelength in diameter, also surrounded by a shield. Often, they are constructed from coax. There is a gap in the shield somewhere. Feedpoint arrangements differ among…
Phil Frost - W8II
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14
votes
4 answers
Is is possible to operate D-Star from a software-defined radio?
What is preventing a software-defined radio from transmitting the D-Star protocol?
Paul V
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14
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7 answers
What is the impedance of an end-fed half-wave antenna?
It is my understanding that the feed-point impedance ($Z_a$) of an end-fed half-wave antenna is dependent on at least the following factors:
$L_a$: The length of the radiating element of the antenna.
$D_a$: The diameter of the radiating element of…
Robert Quattlebaum
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14
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8 answers
Why are Wullenweber CDAAs obsolete?
Wullenweber circularly-disposed antenna arrays (CDAAs) are large HF direction-finding antennas, sometimes colloquially referred to as "elephant cages", that were popular in the Cold War. They allowed the bearing of an incoming signal to be located…
rclocher3
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14
votes
5 answers
How to operate IEEE 802.11 WiFi AP within the amateur radio service?
How can I properly use my ham radio license to operate an IEEE 802.11 WiFi access point within the US amateur radio service, rather than the US "part 15" regulations for unlicensed transmissions?
David Anastasio
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14
votes
4 answers
How can RF exposure hurt you?
In studying for the exam, one question came up about RF Exposure.
G0A
07
What effect does transmitter duty cycle have when evaluating RF exposure?
My understanding of Radio is that it is non ionizing electromagnetic radiation. How can RF be…
spuder
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14
votes
3 answers
Is there a KML or similar file that shows all of the CQ Zones?
I'm wanting to view the CQ Zones in Google Earth, and I understand that a KML file will allow me to do so. Is there a place where I can get a KML file that shows all of the CQ Zones?
PearsonArtPhoto
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14
votes
3 answers
Why do concurrent FM signals not mix together?
Generally when I hear two conflicting signals they do not mix together, but rather one dominates then the other. This phenomenon can be observed on FM broadcast station when driving out of range from one station into the range of another. During the…
Dan
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14
votes
1 answer
Why does the audio on my FM transceiver cut out every 5.5 seconds?
Specifically, my Icom ID-4100a.
What's interesting, is that this happens in MR and VFO modes... but NOT when using the built-in WX stations. For example listening to WX-01 (162.550 MHz), no problem. Listening to 162.550 via VFO and I get the…
webmarc
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14
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4 answers
Calling a friend on simplex
Can someone please help clarify. I have tried searching all over, but almost all of the examples you find online and in books are for calling CQ on HF. I am new to ham radio, and recently got a few of my buddies licensed as well. I am confused over…
Atomiklan
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14
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1 answer
How would a time-difference-of-arrival receiver with two antennas know which side the signal is from?
An easy TDOA design by Byonics was published with the following schematic:
It appears that the antennas are switched at a rate of 640Hz, which allows a 640Hz tone to be heard in the radio when the antennas are not in phase. When the antennas are…
Adam Davis
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14
votes
1 answer
How do I change my registered address with the FCC?
I just moved, and I want to change my registered address with my call-sign.
Is there a form or something somewhere that I can fill out?
Do I have to mail it, or can I turn it in to the FCC or something electronically?
Does it cost anything?
What…
Skyler 440
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14
votes
5 answers
How can I tell if a call sign is valid?
Many different countries have different callsign formats. The US call signs typically fit into a very well defined category, but there are exceptions even there. I'm looking for a way to tell if a call sign is a real call sign, that works with…
PearsonArtPhoto
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14
votes
6 answers
Why are vacuum tubes still used in amateur radios?
I wonder, even in this modern generation why the outdated vacuum tubes are used. In other electronic circuits they have been replaced by more efficient (and small) transistors years ago. Why they are still used?
Sumithran
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13
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1 answer
How can I calculate the effects of an LNA, antenna gain, etc. on noise performance?
There are many things I might do enable my station to hear weaker signals that would otherwise be buried in noise. Just a few possibilities:
Install a nice LNA
Increase antenna gain
Reduce feedline losses
Buy a better receiver
Move to a quieter…
Phil Frost - W8II
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